U.S. patent application number 13/950906 was filed with the patent office on 2014-08-28 for bias circuit and amplifier controlling bias voltage.
This patent application is currently assigned to SAMSUNG ELECTRO-MECHANICS CO., LTD.. The applicant listed for this patent is SAMSUNG ELECTRO-MECHANICS CO., LTD.. Invention is credited to Myeong Woo HAN, Shinichi IIZUKA, Ki Joong KIM, Youn Suk KIM, Ju Young PARK, Jun Goo WON.
Application Number | 20140240049 13/950906 |
Document ID | / |
Family ID | 51387539 |
Filed Date | 2014-08-28 |
United States Patent
Application |
20140240049 |
Kind Code |
A1 |
WON; Jun Goo ; et
al. |
August 28, 2014 |
BIAS CIRCUIT AND AMPLIFIER CONTROLLING BIAS VOLTAGE
Abstract
There are provided a bias circuit and an amplifier controlling a
bias voltage, the bias circuit and the amplifier including a
control voltage generating unit generating a control voltage using
a reference voltage, a bias voltage generating unit generating a
bias voltage according to the control voltage, and a voltage drop
unit dropping the bias voltage from the bias voltage generating
unit to a base voltage so as to provide the base voltage to an
amplifying unit, wherein the control voltage generating unit
controls the control voltage according to an amplitude of a
high-frequency signal input to the amplifying unit.
Inventors: |
WON; Jun Goo; (Suwon,
KR) ; KIM; Ki Joong; (Suwon, KR) ; HAN; Myeong
Woo; (Suwon, KR) ; IIZUKA; Shinichi; (Suwon,
KR) ; PARK; Ju Young; (Suwon, KR) ; KIM; Youn
Suk; (Suwon, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SAMSUNG ELECTRO-MECHANICS CO., LTD. |
Suwon |
|
KR |
|
|
Assignee: |
SAMSUNG ELECTRO-MECHANICS CO.,
LTD.
Suwon
KR
|
Family ID: |
51387539 |
Appl. No.: |
13/950906 |
Filed: |
July 25, 2013 |
Current U.S.
Class: |
330/296 |
Current CPC
Class: |
H03F 3/19 20130101; H03F
2200/78 20130101; H03F 2200/222 20130101; H03F 2200/555 20130101;
H03F 2200/387 20130101; H03F 1/56 20130101; H03F 3/245 20130101;
H03F 1/0272 20130101 |
Class at
Publication: |
330/296 |
International
Class: |
H03F 3/19 20060101
H03F003/19 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 28, 2013 |
KR |
10-2013-0022249 |
Claims
1. A bias circuit, comprising: a control voltage generating unit
generating a control voltage using a reference voltage; a bias
voltage generating unit generating a bias voltage according to the
control voltage; and a voltage drop unit dropping the bias voltage
from the bias voltage generating unit to a base voltage so as to
provide the base voltage to an amplifying unit, wherein the control
voltage generating unit controls the control voltage according to
an amplitude of a high-frequency signal input to the amplifying
unit.
2. The bias circuit of claim 1, wherein the control voltage
generating unit includes a variable resistance circuit having a
resistance value varied depending on a mode voltage determined
according to the amplitude of the high-frequency signal, and the
variable resistance circuit controls the control voltage according
to the varied resistance value.
3. The bias circuit of claim 1, wherein the control voltage
generating unit includes: a variable collector resistor circuit
unit having one terminal connected to an input terminal of the
reference voltage and the other terminal, and having a resistance
value varied depending on a mode voltage determined according to
the amplitude of the high-frequency signal; a first temperature
compensation transistor having a collector connected to the other
terminal of the variable collector resistor circuit unit and an
emitter and a base connected to a ground; a second temperature
compensation transistor having a collector connected to an input
terminal of an operating voltage, a base connected to the collector
of the first temperature compensation transistor, and an emitter
connected to the base of the first temperature compensation
transistor; and an emitter resistor connected between the emitter
of the second temperature compensation transistor and the ground,
and the control voltage output from the collector of the first
temperature compensation transistor is controlled according to the
resistance value varied in the variable collector resistor circuit
unit.
4. The bias circuit of claim 1, wherein the control voltage
generating unit includes: a collector resistor having one terminal
connected to an input terminal of the reference voltage and the
other terminal; a first temperature compensation transistor having
a collector connected to the other terminal of the collector
resistor and an emitter and a base connected to a ground; a second
temperature compensation transistor having a collector connected to
an input terminal of an operating voltage, a base connected to the
collector of the first temperature compensation transistor, and an
emitter connected to the base of the first temperature compensation
transistor; and a variable emitter resistor circuit unit connected
between the emitter of the second temperature compensation
transistor and the ground, and having a resistance value varied
depending on a mode voltage determined according to the amplitude
of the high-frequency signal, and the control voltage output from
the collector of the first temperature compensation transistor is
controlled according to the resistance value varied in the variable
emitter resistor circuit unit.
5. The bias circuit of claim 1, wherein the control voltage
generating unit includes: a variable collector resistor circuit
unit having one terminal connected to an input terminal of the
reference voltage and the other terminal, and having a resistance
value varied depending on a mode voltage determined according to
the amplitude of the high-frequency signal; a first temperature
compensation transistor having a collector connected to the other
terminal of the variable collector resistor circuit unit and an
emitter and a base connected to a ground; a second temperature
compensation transistor having a collector connected to an input
terminal of an operating voltage, a base connected to the collector
of the first temperature compensation transistor, and an emitter
connected to the base of the first temperature compensation
transistor; and a variable emitter resistor circuit unit connected
between the emitter of the second temperature compensation
transistor and the ground, and having a resistance value varied
depending on a mode voltage determined according to the amplitude
of the high-frequency signal, and the control voltage output from
the collector of the first temperature compensation transistor is
controlled according to the resistance value varied in each of the
variable collector resistor circuit unit and the variable emitter
resistor circuit unit.
6. The bias circuit of claim 5, wherein the variable collector
resistor circuit unit includes: a plurality of resistors connected
in series between the one terminal and the other terminal thereof;
and a first semiconductor switch element connected to at least one
of the plurality of resistors in parallel and turned on or off
depending on the mode voltage.
7. The bias circuit of claim 5, wherein the variable emitter
resistor circuit unit includes: a plurality of resistors connected
in series between the emitter of the second temperature
compensation transistor and the ground; and a second semiconductor
switch element connected to at least one of the plurality of
resistors in parallel and turned on or off depending on the mode
voltage.
8. The circuit of claim 1, wherein the bias voltage generating unit
includes: a bias supplying transistor having a collector connected
to an input terminal of an operating voltage, a base connected to
the collector of the first temperature compensating transistor, and
an emitter connected to an output node of the bias voltage
generating unit; and a capacitor connected between the base of the
bias supplying transistor and a ground.
9. An amplifier, comprising: an amplifying unit amplifying a
high-frequency signal; a control voltage generating unit generating
a control voltage using a reference voltage, the control voltage
being controlled depending on a mode voltage; a bias voltage
generating unit generating a bias voltage according to the control
voltage; a voltage drop unit dropping the bias voltage from the
bias voltage generating unit to a base voltage so as to provide the
base voltage to the amplifying unit; and a control unit determining
the mode voltage according to the amplitude of the high-frequency
signal so as to provide the mode voltage to the control voltage
generating unit.
10. The amplifier of claim 9, wherein the control voltage
generating unit includes a variable resistance circuit having a
resistance value varied depending on the mode voltage, and the
variable resistance circuit controls the control voltage according
to the varied resistance value.
11. The amplifier of claim 9, wherein the control voltage
generating unit includes: a variable collector resistor circuit
unit having one terminal connected to an input terminal of the
reference voltage and the other terminal, and having a resistance
value varied depending on the mode voltage; a first temperature
compensation transistor having a collector connected to the other
terminal of the variable collector resistor circuit unit and an
emitter and a base connected to a ground; a second temperature
compensation transistor having a collector connected to an input
terminal of an operating voltage, a base connected to the collector
of the first temperature compensation transistor, and an emitter
connected to the base of the first temperature compensation
transistor; and an emitter resistor connected between the emitter
of the second temperature compensation transistor and the ground,
and the control voltage output from the collector of the first
temperature compensation transistor is controlled according to the
resistance value varied in the variable collector resistor circuit
unit.
12. The amplifier of claim 9, wherein the control voltage
generating unit includes: a collector resistor having one terminal
connected to an input terminal of the reference voltage and the
other terminal; a first temperature compensation transistor having
a collector connected to the other terminal of the collector
resistor and an emitter and a base connected to a ground; a second
temperature compensation transistor having a collector connected to
an input terminal of an operating voltage, a base connected to the
collector of the first temperature compensation transistor, and an
emitter connected to the base of the first temperature compensation
transistor; and a variable emitter resistor circuit unit connected
between the emitter of the second temperature compensation
transistor and the ground, and having a resistance value varied
depending on the mode voltage, and the control voltage output from
the collector of the first temperature compensation transistor is
controlled according to the resistance value varied in the variable
emitter resistor circuit unit.
13. The amplifier of claim 9, wherein the control voltage
generating unit includes: a variable collector resistor circuit
unit having one terminal connected to an input terminal of the
reference voltage and the other terminal, and having a resistance
value varied depending on a mode voltage; a first temperature
compensation transistor having a collector connected to the other
terminal of the variable collector resistor circuit unit and an
emitter and a base connected to a ground; a second temperature
compensation transistor having a collector connected to an input
terminal of an operating voltage, a base connected to the collector
of the first temperature compensation transistor, and an emitter
connected to the base of the first temperature compensation
transistor; and a variable emitter resistor circuit unit connected
between the emitter of the second temperature compensation
transistor and the ground, and having a resistance value varied
depending on the mode voltage, and the control voltage output from
the collector of the first temperature compensation transistor is
controlled according to the resistance value varied in each of the
variable collector resistor circuit unit and in the variable
emitter resistor circuit unit.
14. The amplifier of claim 13, wherein the variable collector
resistor circuit unit includes: a plurality of resistors connected
in series between the one terminal and the other terminal thereof;
and a first semiconductor switch element connected to at least one
of the plurality of resistors in parallel and turned on or off
depending on the mode voltage.
15. The amplifier circuit of claim 13, wherein the variable emitter
resistor circuit unit includes: a plurality of resistors connected
in series between the emitter of the second temperature
compensation transistor and the ground; and a second semiconductor
switch element connected to at least one of the plurality of
resistors in parallel and turned on or off depending on the mode
voltage.
16. The amplifier of claim 9, wherein the bias voltage generating
unit includes: a bias supplying transistor having a collector
connected to an input terminal of an operating voltage, a base
connected to the collector of the first temperature compensating
transistor, and an emitter connected to an output node of the bias
voltage generating unit; and a capacitor connected between the base
of the bias supplying transistor and a ground.
17. The amplifier of claim 9, wherein the control unit includes: a
signal detecting unit detecting a voltage of the amplitude of the
high-frequency signal output from the amplifying unit so as to
provide the detected voltage; and a comparator unit comparing the
detected voltage with a comparison reference voltage and outputting
the mode voltage based on the comparison result.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the priority of Korean Patent
Application No. 10-2013-0022249 filed on Feb. 28, 2013, in the
Korean Intellectual Property Office, the disclosure of which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a bias circuit and an
amplifier capable of controlling a bias voltage according to the
amplitude of a high-frequency signal input thereto.
[0004] 2. Description of the Related Art
[0005] In general, a digital modulation/demodulation scheme has
been selected as a wireless communications scheme, and appropriate
schemes have been employed in consideration of frequency
utilization efficiency. For instance, a quadrature phase shift
keying (QPSK) scheme is employed for mobile telephones using a code
division multiple access (CDMA) scheme, while an orthogonal
frequency division multiplexing (QFDM) scheme is employed in a
wireless LAN conforming to the Institute of Electrical and
Electronics Engineers (IEEE) 802.11 standard.
[0006] Wireless communications systems in which such wireless
communications schemes are employed include power amplifiers for
amplifying high-frequency signals.
[0007] Here, in a system requiring linear amplification, a power
amplifier having linear characteristics for amplifying a
transmission signal without distortion is needed. Here, linear
characteristics means that the power of an output signal is
amplified at a constant rate while the phase thereof is not
changed, even in the case that the power of an input signal
varies.
[0008] In addition, a technology which compensates for temperature
so as to prevent a power amplification rate from being
significantly changed, even if an ambient temperature changes, is
required.
[0009] In an existing power amplifier, a bias voltage generated by
a bias circuit is supplied to a power amplifying element. The bias
circuit may include a temperature compensation function.
[0010] In the existing power amplifier, a bias voltage and a bias
current are provided to the base of an amplifying transistor
included in an amplifying circuit so as to amplify a high-frequency
signal input thereto.
[0011] Although the existing power amplifier has a temperature
compensation function using a transistor included in the bias
circuit, the temperature compensation function thereof may also be
limited, such that the bias current may increase as temperature
increases. In this case, the increased bias current may in turn
cause the temperature at the junction of the transistor included in
the bias circuit to be increased, such that the so-called "thermal
runaway" phenomenon may occur.
[0012] In order to overcome this shortcoming, a current limiting
resistor for limiting the bias current may be provided between the
current supplying terminal of the bias circuit and the base of the
amplifying transistor.
[0013] However, in the existing power amplifier, when a
high-frequency signal having a higher amplitude than a normal
amplitude is input thereto, the bias current increases according to
the characteristics of the amplifying transistor. As the bias
current increases, the voltage drop across the current limiting
resistor is increased, such that the voltage supplied to the base
of the amplifying transistor may be reduced.
[0014] As described above, when a high-frequency signal having a
relatively large amplitude is input, the bias voltage supplied to
the base of the amplifying transistor may be reduced, such that a
linear region in which the amplifying transistor may perform
amplification without distortion is narrowed. As a result, the
high-frequency signal having a large amplitude may be
distorted.
[0015] Patent Document 1 referenced below relates to a power
amplifier but does not teach controlling a bias voltage according
to the amplitude of a high-frequency signal.
RELATED ART DOCUMENT
[0016] (Patent Document 1) Japanese Patent Laid-Open Publication
No. 2009-200770
SUMMARY OF THE INVENTION
[0017] An aspect of the present invention provides a bias circuit
and an amplifier capable of controlling a bias voltage according to
an amplitude of a high-frequency signal input thereto.
[0018] According to an aspect of the present invention, there is
provided a bias circuit, including: a control voltage generating
unit generating a control voltage using a reference voltage; a bias
voltage generating unit generating a bias voltage according to the
control voltage; and a voltage drop unit dropping the bias voltage
from the bias voltage generating unit to a base voltage so as to
provide the base voltage to an amplifying unit, wherein the control
voltage generating unit controls the control voltage according to
an amplitude of a high-frequency signal input to the amplifying
unit.
[0019] The control voltage generating unit may include a variable
resistance circuit having a resistance value varied depending on a
mode voltage determined according to the amplitude of the
high-frequency signal, and the variable resistance circuit may
control the control voltage according to the varied resistance
value.
[0020] The control voltage generating unit may include: a variable
collector resistor circuit unit having one terminal connected to an
input terminal of the reference voltage and the other terminal, and
having a resistance value varied depending on a mode voltage
determined according to the amplitude of the high-frequency signal;
a first temperature compensation transistor having a collector
connected to the other terminal of the variable collector resistor
circuit unit and an emitter and a base connected to a ground; a
second temperature compensation transistor having a collector
connected to an input terminal of an operating voltage, a base
connected to the collector of the first temperature compensation
transistor, and an emitter connected to the base of the first
temperature compensation transistor; and an emitter resistor
connected between the emitter of the second temperature
compensation transistor and the ground, and the control voltage
output from the collector of the first temperature compensation
transistor may be controlled according to the resistance value
varied in the variable collector resistor circuit unit.
[0021] The control voltage generating unit may include: a collector
resistor having one terminal connected to an input terminal of the
reference voltage and the other terminal; a first temperature
compensation transistor having a collector connected to the other
terminal of the collector resistor and an emitter and a base
connected to a ground; a second temperature compensation transistor
having a collector connected to an input terminal of an operating
voltage, a base connected to the collector of the first temperature
compensation transistor, and an emitter connected to the base of
the first temperature compensation transistor; and a variable
emitter resistor circuit unit connected between the emitter of the
second temperature compensation transistor and the ground, and
having a resistance value varied depending on a mode voltage
determined according to the amplitude of the high-frequency signal,
and the control voltage output from the collector of the first
temperature compensation transistor may be controlled according to
the resistance value varied in the variable emitter resistor
circuit unit.
[0022] The control voltage generating unit may include: a variable
collector resistor circuit unit having one terminal connected to an
input terminal of the reference voltage and the other terminal, and
having a resistance value varied depending on a mode voltage
determined according to the amplitude of the high-frequency signal;
a first temperature compensation transistor having a collector
connected to the other terminal of the variable collector resistor
circuit unit and an emitter and a base connected to a ground; a
second temperature compensation transistor having a collector
connected to an input terminal of an operating voltage, a base
connected to the collector of the first temperature compensation
transistor, and an emitter connected to the base of the first
temperature compensation transistor; and a variable emitter
resistor circuit unit connected between the emitter of the second
temperature compensation transistor and the ground, and having a
resistance value varied depending on a mode voltage determined
according to the amplitude of the high-frequency signal, and the
control voltage output from the collector of the first temperature
compensation transistor may be controlled according to the
resistance value varied in each of the variable collector resistor
circuit unit and the variable emitter resistor circuit unit.
[0023] According to another aspect of the present invention, there
is provided an amplifier, including: an amplifying unit amplifying
a high-frequency signal; a control voltage generating unit
generating a control voltage using a reference voltage, the control
voltage being controlled depending on a mode voltage; a bias
voltage generating unit generating a bias voltage according to the
control voltage; a voltage drop unit dropping the bias voltage from
the bias voltage generating unit to a base voltage so as to provide
the base voltage to the amplifying unit; and a control unit
determining the mode voltage according to the amplitude of the
high-frequency signal so as to provide the mode voltage to the
control voltage generating unit.
[0024] The control voltage generating unit may include a variable
resistance circuit having a resistance value varied depending on
the mode voltage and the variable resistance circuit may control
the control voltage according to the varied resistance value.
[0025] The control voltage generating unit may include: a variable
collector resistor circuit unit having one terminal connected to an
input terminal of the reference voltage and the other terminal, and
having a resistance value varied depending on the mode voltage; a
first temperature compensation transistor having a collector
connected to the other terminal of the variable collector resistor
circuit unit and an emitter and a base connected to a ground; a
second temperature compensation transistor having a collector
connected to an input terminal of an operating voltage, a base
connected to the collector of the first temperature compensation
transistor, and an emitter connected to the base of the first
temperature compensation transistor; and an emitter resistor
connected between the emitter of the second temperature
compensation transistor and the ground, and the control voltage
output from the collector of the first temperature compensation
transistor may be controlled according to the resistance value
varied in the variable collector resistor circuit unit.
[0026] The control voltage generating unit may include: a collector
resistor having one terminal connected to an input terminal of the
reference voltage and the other terminal; a first temperature
compensation transistor having a collector connected to the other
terminal of the collector resistor and an emitter and a base
connected to a ground; a second temperature compensation transistor
having a collector connected to an input terminal of an operating
voltage, a base connected to the collector of the first temperature
compensation transistor, and an emitter connected to the base of
the first temperature compensation transistor; and a variable
emitter resistor circuit unit connected between the emitter of the
second temperature compensation transistor and the ground, and
having a resistance value varied depending on the mode voltage, and
the control voltage output from the collector of the first
temperature compensation transistor may be controlled according to
the resistance value varied in the variable emitter resistor
circuit unit.
[0027] The control voltage generating unit may include: a variable
collector resistor circuit unit having one terminal connected to an
input terminal of the reference voltage and the other terminal, and
having a resistance value varied depending on a mode voltage; a
first temperature compensation transistor having a collector
connected to the other terminal of the variable collector resistor
circuit unit and an emitter and a base connected to a ground; a
second temperature compensation transistor having a collector
connected to an input terminal of an operating voltage, a base
connected to the collector of the first temperature compensation
transistor, and an emitter connected to the base of the first
temperature compensation transistor; and a variable emitter
resistor circuit unit connected between the emitter of the second
temperature compensation transistor and the ground, and having a
resistance value varied depending on the mode voltage, and the
control voltage output from the collector of the first temperature
compensation transistor may be controlled according to the
resistance value varied in each of the variable collector resistor
circuit unit and in the variable emitter resistor circuit unit.
[0028] The variable collector resistor circuit unit may include: a
plurality of resistors connected in series between the one terminal
and the other terminal thereof; and a first semiconductor switch
element connected to at least one of the plurality of resistors in
parallel and turned on or off depending on the mode voltage.
[0029] The variable emitter resistor circuit unit may include: a
plurality of resistors connected in series between the emitter of
the second temperature compensation transistor and the ground; and
a second semiconductor switch element connected to at least one of
the plurality of resistors in parallel and turned on or off
depending on the mode voltage.
[0030] The bias voltage generating unit may include: a bias
supplying transistor having a collector connected to an input
terminal of an operating voltage, a base connected to the collector
of the first temperature compensating transistor, and an emitter
connected to an output node of the bias voltage generating unit;
and a capacitor connected between the base of the bias supplying
transistor and a ground.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] The above and other aspects, features and other advantages
of the present invention will be more clearly understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0032] FIG. 1 is a block diagram of a bias circuit and an amplifier
according to an embodiment of the present invention;
[0033] FIG. 2 is a block diagram of a bias circuit and an amplifier
according to another embodiment of the present invention;
[0034] FIG. 3 is a circuit diagram illustrating an implementation
example of the bias circuit and the amplifier according to the
embodiment of the present invention;
[0035] FIG. 4 is a circuit diagram illustrating another
implementation example of the bias circuit and the amplifier
according to the embodiment of the present invention;
[0036] FIG. 5 is a circuit diagram illustrating another
implementation example of the bias circuit and the amplifier
according to the embodiment of the present invention;
[0037] FIG. 6 is a diagram illustrating an implementation example
of a control unit according to the embodiment of the present
invention;
[0038] FIG. 7 is a circuit diagram illustrating an implementation
example of a control voltage generating unit according to the
embodiment of the present invention;
[0039] FIG. 8 is a circuit diagram illustrating another
implementation example of the control voltage generating unit
according to the embodiment of the present invention;
[0040] FIG. 9 is a circuit diagram illustrating another
implementation example of the control voltage generating unit
according to the embodiment of the present invention; and
[0041] FIG. 10 is a graph showing an EVM to average output power
characteristics of the amplifier according to the embodiment of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0042] Hereinafter, embodiments of the present invention will be
described in detail with reference to the accompanying drawings.
The invention may, however, be embodied in many different forms and
should not be construed as being limited to the embodiments set
forth herein. Rather, these embodiments are provided so that this
disclosure will be thorough and complete, and will fully convey the
scope of the invention to those skilled in the art. In the
drawings, the shapes and dimensions of elements may be exaggerated
for clarity, and the same reference numerals will be used
throughout to designate the same or like elements.
[0043] FIG. 1 is a block diagram of a bias circuit and an amplifier
according to an embodiment of the present invention. FIG. 2 is a
block diagram of a bias circuit and an amplifier according to
another embodiment of the present invention.
[0044] Referring to FIG. 1, the bias circuit and the amplifier
according to the embodiment of the present invention may include a
control voltage generating unit 100, a bias voltage generating unit
200, and a voltage drop unit 300.
[0045] Referring to FIG. 2, the bias circuit and the amplifier
according to another embodiment of the present invention may
include the control voltage generating unit 100, the bias voltage
generating unit 200, the voltage drop unit 300, and a control unit
400.
[0046] In addition, referring to FIGS. 1 and 2, the amplifier
according to the embodiments of the present invention may further
include an amplifying unit 52 amplifying a high-frequency signal,
an input matching unit 51 connected to an input terminal of the
amplifying unit 52, and an output matching unit 53 connected to an
output terminal of the amplifying unit 52.
[0047] The control voltage generating unit 100 may generate a
control voltage Vc using a reference voltage Vref. For example,
when the reference voltage Vref is 2.9 V, the control voltage Vc
may be 2.6 V.
[0048] Here, the control voltage generating unit 100 may control
the control voltage Vc depending on the amplitude of a
high-frequency signal input to the amplifying unit 52.
[0049] The bias voltage generating unit 200 may generate a bias
voltage Vbias according to the control voltage Vc. For example, due
to the operation of a transistor included in the bias voltage
generating unit 200, when the control voltage Vc supplied to a base
of the transistor increases, the bias voltage Vbias increases
accordingly, and when the control voltage Vc decreases, the bias
voltage Vbias decreases accordingly.
[0050] The voltage drop unit 300 may drop the bias voltage Vbias
from the bias voltage generating unit 200 to a base voltage Vbase
so as to provide the base voltage Vbase to the amplifying unit
52.
[0051] For instance, the voltage drop unit 300 may include a
resistor connected between an output node No of the bias voltage
generating unit 200 and an input node Nb of the amplifying unit
52.
[0052] Then, the amplifying unit 52 may receive the base voltage
Vbase from the voltage drop unit 300 so as to amplify the power of
the high-frequency signal.
[0053] Here, the input matching unit 51 performs impedance matching
in the input terminal of the amplifying unit 52, such that a
high-frequency signal via an input terminal IN is transmitted to
the amplifying unit 52 without loss thereof. Likewise, the output
matching unit 53 performs impedance matching in the output terminal
of the amplifying unit 52, such that a signal output from the
amplifying unit 52 is transmitted to an output terminal OUT without
loss thereof.
[0054] The control unit 400 may determine a mode voltage Vmode
depending on the amplitude of a high-frequency signal output from
the amplifying unit 52 so as to provide it to the control voltage
generating unit 100.
[0055] In particular, the control voltage generating unit 100 may
include a variable resistance circuit having a resistance value
varied depending on the mode voltage Vmode determined according to
the amplitude of the high-frequency signal. Here, the variable
resistance circuit may control the control voltage Vc according to
the varied resistance value.
[0056] Now, the bias circuit and the amplifier including the
control voltage generating unit 100 will be described with
reference to FIGS. 3 to 5.
[0057] FIG. 3 is a circuit diagram illustrating an implementation
example of the bias circuit and the amplifier according to the
embodiment of the present invention.
[0058] Referring to FIG. 3, the control voltage generating unit 100
may include a variable collector resistor circuit unit 110 having
one terminal T11 connected to the input terminal of the reference
voltage Vref and the other terminal T12. The variable collector
resistor circuit unit 110 may have a resistance value varied
depending on the mode voltage Vmode determined according to the
amplitude of the high-frequency signal.
[0059] Further, the control voltage generating unit 100 may include
a first temperature compensating transistor Q11 having a collector
connected to the other terminal T12 of the variable collector
resistor circuit unit 110 and an emitter and a base connected to a
ground; and a second temperature compensation transistor Q12 having
a collector connected to an input terminal of an operating voltage
Vcc, a base connected to the collector of the first temperature
compensation transistor Q11 and an emitter connected to the base of
the first temperature compensation transistor Q11; and an emitter
resistor R12 connected between the emitter of the second
temperature compensation transistor Q12 and the ground.
[0060] In this configuration, in accordance with the varied
resistance value of the variable collector resistor circuit unit
110, the control voltage Vc output from the collector of the first
temperature compensation transistor Q11 may be controlled.
[0061] Here, a base-emitter voltage Vbe1 of the first temperature
compensating transistor Q11 is equal to the voltage VR12 across the
emitter resistor R12, and a collector-base voltage Vcb1 of the
first temperature compensation transistor Q11 is equal to a
base-emitter voltage Vbe2 of the second temperature compensation
transistor Q12.
[0062] The control voltage Vc output from the collector of the
first temperature compensating transistor Q11 is equal to the sum
of the collector-base voltage Vcb1 and the base-emitter voltage
Vbe1 of the first temperature compensation transistor Q11, and is
equal to the sum of the base-emitter voltage Vb2 of the second
temperature compensation transistor Q12 and the voltage VR12 across
the emitter resistor R12.
[0063] FIG. 4 is a circuit diagram illustrating another
implementation example of the bias circuit and the amplifier
according to the embodiment of the present invention.
[0064] Referring to FIG. 4, the control voltage generating unit 100
may include a collector resistor R11 having one terminal T11
connected to the input terminal of the reference voltage Vref and
the other terminal T12; a first temperature compensating transistor
Q11 having a collector connected to the other terminal T12 of the
collector resistor R11 and an emitter and a base connected to a
ground; and a second temperature compensation transistor Q12 having
a collector connected to an input terminal of an operating voltage
Vcc, a base connected to the collector of the first temperature
compensation transistor Q11 and an emitter connected to the base of
the first temperature compensation transistor Q11.
[0065] Further, the control voltage generating unit 100 may include
a variable emitter resistor circuit unit 120, which is connected
between the emitter of the second temperature compensation
transistor Q12 and a ground and has a resistance value varied
depending on the mode voltage Vmode determined according to the
amplitude of the high-frequency signal.
[0066] In this configuration, in accordance with the varied
resistance value of the variable emitter resistor circuit unit 120,
the control voltage Vc output from the collector of the first
temperature compensation transistor Q11 may be controlled.
[0067] FIG. 5 is a circuit diagram illustrating another
implementation example of the bias circuit and the amplifier
according to the embodiment of the present invention.
[0068] Referring to FIG. 5, the control voltage generating unit 100
may include a variable collector resistor circuit unit 110 having
one terminal T11 connected to an input terminal of the reference
voltage Vref and the other terminal T12. The variable collector
resistor circuit unit 110 may have a resistance value varied
depending on the mode voltage Vmode determined according to the
amplitude of the high-frequency signal.
[0069] Further, the control voltage generating unit 100 may include
a first temperature compensating transistor Q11 having a collector
connected to the other terminal T12 of the collector resistor R11
and an emitter and a base connected to a ground; and a second
temperature compensation transistor Q12 having a collector
connected to an input terminal of an operating voltage Vcc, a base
connected to the collector of the first temperature compensation
transistor Q11 and an emitter connected to the base of the first
temperature compensation transistor Q11.
[0070] Further, the control voltage generating unit 100 may include
a variable emitter resistor circuit unit 120 connected between the
emitter of the second temperature compensation transistor Q12 and
the ground. The variable emitter resistor circuit unit 120 may have
a resistance value varied depending on the mode voltage Vmode
determined according to the amplitude of the high-frequency
signal.
[0071] In this configuration, in accordance with the varied
resistance values of the variable collector resistor circuit unit
110 and the emitter resistor circuit unit 120, the control voltage
Vc output from the collector of the first temperature compensation
transistor Q11 may be controlled.
[0072] Referring to FIGS. 4 and 5, the base-emitter voltage Vbe1 of
the first temperature compensating transistor Q11 is equal to the
voltage VR12 across the emitter resistor R12, and the
collector-base voltage Vcb1 of the first temperature compensation
transistor Q11 is equal to the base-emitter voltage Vbe2 of the
second temperature compensation transistor Q12.
[0073] The control voltage Vc output from the collector of the
first temperature compensating transistor Q11 is equal to the sum
of the collector-base voltage Vcb1 and the base-emitter voltage
Vbe1 of the first temperature compensation transistor Q11, and is
equal to the sum of the base-emitter voltage Vbe2 of the second
temperature compensation transistor Q12 and the voltage VR12 across
the variable emitter resistor circuit unit 120.
[0074] In addition, the bias voltage generating unit 200 may
include a bias supplying transistor Q21 having a collector
connected to the input terminal of the operating voltage Vcc, a
base connected to the collector of the first temperature
compensating transistor Q11 and an emitter connected to the output
node of the bias voltage generating unit 200; and a capacitor C21
connected between the base of the bias supplying transistor Q21 and
a ground.
[0075] Here, the bias supplying transistor Q21 allows an amount of
the current proportional to the amplitude of the control voltage Vc
to flow between the collector and the emitter of the bias supplying
transistor Q21.
[0076] Subsequently, the current flowing between the collector and
the emitter of the bias supplying transistor Q21 flows through the
voltage drop unit 300 and in this case, voltage drop occurs in the
voltage drop unit 300. Here, the voltage drop unit 300 may include
a resistor.
[0077] FIG. 6 is a diagram illustrating an implementation example
of a control unit according to the embodiment of the present
invention.
[0078] Referring to FIG. 6, the control unit 400 may include a
signal detecting unit 410 and a comparator unit 420.
[0079] The signal detecting unit 410 may detect a voltage of the
amplitude of a high-frequency signal output from the amplifying
unit 52 so as to provide the detected voltage Vd to the comparator
unit 420.
[0080] The comparator 420 may compare the detected voltage Vd with
a comparison reference voltage V1 so as to output the mode voltage
Vmode based on the result.
[0081] Here, the comparator unit may include an operational
amplifier OP1 having a non-inverting input terminal to which the
detected voltage Vd is input and an inverting input terminal to
which the comparison reference voltage V1 is input. Here, the
comparison reference voltage V1 may set to the voltage at which
average output power of a high-frequency signal is 14 dB.
[0082] For example, the comparator unit 420 may output the mode
voltage Vmode having a low level when the input high-frequency
signal has an amplitude smaller than a normal amplitude.
Alternatively, the comparator unit 420 may output the mode voltage
Vmode having a high level when the input high-frequency signal has
an amplitude greater than normal amplitude.
[0083] FIG. 7 is a circuit diagram illustrating an implementation
example of a control voltage generating unit according to the
embodiment of the present invention. FIG. 8 is a circuit diagram
illustrating another implementation example of the control voltage
generating unit according to the embodiment of the present
invention. FIG. 9 is a circuit diagram illustrating another
implementation example of the control voltage generating unit
according to the embodiment of the present invention.
[0084] The variable collector resistor circuit unit 110 may include
a plurality of resistors R11-1 and R11-2 connected in series
between the one terminal T11 and the other terminal T12, and a
first semiconductor switch element SW1 connected to at least one of
the plurality of resistors R11-1 and R11-2 in parallel and turned
on or off depending on the mode voltage Vmode.
[0085] Here, the variable collector resistor circuit unit 110 is
not limited to the implementation example but may be variously
implemented as a serial resistor circuit, a parallel resistor
circuit or a combination of serial or parallel resistor circuit and
a semiconductor switch element.
[0086] For example, when the variable collector resistor circuit
unit 110 includes two resistors R11-1 and R11-2 connected in series
between the one terminal T11 and the other terminal T12 as shown in
FIGS. 7 and 9, the first semiconductor switch element SW1 may be
connected to the resistor R11-1 in parallel. Here, the first
semiconductor switch element SW1 may include a transistor having a
base to which the mode voltage Vmode is input and a collector and
an emitter connected to both terminals of the resistor R11-1,
respectively.
[0087] When a high-frequency signal input thereto is smaller than
normal amplitude, if the mode voltage Vmode is in a low level, then
the first semiconductor switch element SW1 is turned off according
to the mode voltage Vmode at the low level, such that the voltage
dropped across two resistors R11-1 and R11-2 is increased and thus
the control voltage Vc is decreased.
[0088] Alternatively, when a high-frequency signal input thereto is
greater than normal amplitude, if the mode voltage Vmode is in a
high level, then the first semiconductor switch element SW1 is
turned on according to the mode voltage Vmode at the high level,
such that the voltage dropped across one resistor R11-2 is
decreased and thus the control voltage Vc is increased.
[0089] The variable emitter resistor circuit unit 120 may include a
plurality of resistors connected in series between the emitter of
the second temperature compensation transistor Q12 and a ground,
and a second semiconductor switch element connected to at least one
of the plurality of resistors in parallel and turned on or off
depending on the mode voltage Vmode.
[0090] Here, the variable emitter resistor circuit unit 120 is not
limited to the implementation example but may be variously
implemented as a serial resistor circuit, a parallel resistor
circuit or a combination of serial or parallel resistor circuit and
a semiconductor switch element.
[0091] For example, when the variable collector resistor circuit
unit 120 includes two resistors R12-1 and R12-2 connected in series
between the emitter of the second temperature compensation
transistor Q12 and a ground as shown in FIGS. 8 and 9, the second
semiconductor switch element SW2 may be connected to the resistor
R12-2 in parallel. Here, the second semiconductor switch element
SW2 may include a transistor having a base to which the mode
voltage Vmode is input and a collector and an emitter connected to
both terminals of the resistor R12-2, respectively.
[0092] When a high-frequency signal input thereto is smaller than
normal amplitude, if the mode voltage Vmode is in a low level, then
the semiconductor switch element SW2 is turned off according to the
mode voltage Vmode at the low level, such that the voltage dropped
across two resistors R11-1 and R11-2 is increased, and the
base-emitter voltage Vbe2 of the second temperature compensation
transistor Q12 is decreased and thus the control voltage Vc is
decreased.
[0093] Alternatively, when a high-frequency signal input thereto is
greater than normal amplitude, if the mode voltage Vmode is in a
high level, then the first semiconductor switch element SW1 is
turned on according to the mode voltage Vmode at the high level,
such that the voltage dropped across one resistor R11-2 is
decreased, and the base-emitter voltage Vbe2 of the second
temperature compensation transistor Q12 is increased and thus the
control voltage Vc is increased.
[0094] FIG. 10 is a graph showing an EVM to average output power
characteristics of the amplifier according to the embodiment of the
present invention.
[0095] Referring to FIG. 10, in the power amplifier according to
the embodiment of the present invention, the bias circuit unit 300
operates differently depending on the amplitude of an input signal,
thereby facilitating the optimization.
[0096] The linearity of a linear power amplifier may be evaluated
with EVM (%) characteristics, and as EVM (%) is lowered, the
linearity of a linear power amplifier may be improved. Referring to
FIG. 10, compared to the characteristics graph G1 according to the
related art, the characteristics graph G2 according to the
embodiment of the present invention is generally improved, and,
especially, EVM characteristics of the power amplifier according to
the embodiment of the present invention is significantly improved
in terms of low power (below 14 dB).
[0097] As set forth above, according to embodiments of the present
invention, bias voltage can be controlled according to the
amplitude of a high-frequency signal input thereto. Accordingly,
when a high-frequency signal having a relatively large amplitude is
input, the bias voltage is increased so that the high-frequency
signal can be amplified without distortion.
[0098] While the present invention has been shown and described in
connection with the embodiments, it will be apparent to those
skilled in the art that modifications and variations can be made
without departing from the spirit and scope of the invention as
defined by the appended claims.
* * * * *